1. Field of the Invention
The present invention relates generally to semiconductor wafer processing systems, and more particularly to such systems for the transfer of semiconductor wafers to a processing chamber.
2. Related Art
High temperature processing of silicon wafers is important for manufacturing modern microelectronics devices. Such processes, including silicide formation, implant anneals, oxidation, diffusion drive-in and chemical vapor deposition (CVD), may be performed at high temperatures using conventional thermal processing techniques. Furthermore, many microelectronics circuits require feature sizes smaller than one micron and junction depths less than a few hundred angstroms. In order to limit both the lateral and downward diffusion of dopants, as well as to provide a greater degree of control during processing, it is desirable to minimize the duration of high temperature processing.
Semiconductor wafers, flat panel displays, and other similar substrates typically have numerous material layers deposited thereon during device fabrication. Some commonly deposited layers (e.g., spin-on glass (SOG) films) may contain contaminants, defects or undesirable microstructures that can be reduced or removed by heating or “annealing” the substrate at an appropriate temperature for an appropriate time. Other deposited layers (e.g., copper films) may have properties that undesirably change over time or “self-anneal”, resulting in unpredictable deposited layer properties (e.g., unpredictable resistivity, stress, grain size, and hardness). As with contaminants, defects, and undesirable microstructures, deposited layer properties often can be stabilized by a controlled annealing step. Following the annealing step, the substrate preferably is rapidly cooled to stop the annealing process, and so that other processes can be performed on the substrate, in order to increase throughput.
Conventionally, annealing is performed within a quartz furnace that must be slowly pre-heated, such as by lamps, to a desired annealing temperature, or within a rapid thermal process (RTP) system that can be rapidly heated to a desired annealing temperature. Unfortunately, conventional lamp-based RTP systems have considerable drawbacks with regard to uniform temperature distribution. One alternative to lamp-based RTP systems is to use a hot plate annealing to heat the wafer. Such systems are disclosed in commonly-owned U.S. Pat. Nos. 6,809,035 and 6,345,150, both of which are incorporated by reference in their entirety. These systems use a hot plate, which can be heated by heating elements on or adjacent to the plate or plates, positioned below and/or above the wafer. The hot plate enables the wafer to be quickly brought to a desired temperature, such as for annealing.
Thereafter, an annealed substrate is transferred to a separate cooling module that conventionally employs a cooled substrate support and is slightly backfilled with a gas such as helium to enhance thermal conduction. The separate cooling module increases equipment cost and complexity, as well as equipment footprint, and decreases substrate throughput by requiring undesirable substrate transfer time between the heating and cooling systems. Other conventional processing systems have a cooling mechanism within the same chamber as the hot plate, as opposed to in a separate module. Cooling down a heated chamber or heating up a cooled chamber requires additional energy and time.
Accordingly, it is desirable to have a system capable of heating or cooling a wafer for RTP or other processes without disadvantages of conventional systems, discussed above.